The present disclosure is related to methods of covalently attaching functionalized surface treated metallic type pigments to polyester resin for use in forming special effect images, for example using xerographic or electrophotographic printing devices.
A desired goal of electrophotography is to be able to print special effects, such as pearlescent or metallic images. While many commercial specialty pigments exist for pearlescent or metallic effects, their particle size is too large to be incorporated into electrophotographic toner particles. Median pigment sizes for commercial pearlescent/metallic pigments range from 5 to >50 microns, which is similar in size or larger than the electrophotographic toner itself. While the large particle size pigments are needed to produce special optical effects, such as metallic reflectivity, both chemical and conventional toner making processes currently available fail to incorporate these large pigments because it is currently not possible to incorporate such large pigment particles in an emulsion aggregation (EA) toner process.
One attempt to combine specialty pigments with toner is to melt-mix a specialty pigment with a toner resin. However, due to the large size of the specialty pigment, even if the toner were 20 or 30 microns in size, the pigment particles would comprise the bulk of the toner. Thus, it would be extremely difficult to jet or print toner particles including the specialty pigments, as the toner particles would end up very large. Also, with such large pigments, even a 20-30 micron toner would only have at most only a few specialty pigment particles in each particle, making the toner very inhomogeneous and the effect minimally realized. Many toner particles would have no pigment particle in them, while others would have one or merely a few pigment particles.